Document Type


Publication Date



reproductive fertility, herd bulls, beef operations, profitability

Extension Number

ExEx 2066


Agricultural and Biosystems Engineering


Herd bulls have a large influence on many aspects of beef operations, especially an operation’s profitability. For example, percent calf crop weaned is the single most important factor influencing profitability, and the number of cows bred during the breeding season plays the largest role in percent calf crop weaned. Therefore, an operation’s profitability is directly tied to the herd bull’s breeding ca¬pability. In addition, herd bulls supply half of the genetics to all the calves he sires; therefore, bull selection can be the most powerful method of genetic improvement in the herd. Herd bulls also influence overall herd fertility more than any other single animal; the loss of fertility by a bull can mean the potential loss of an entire calf crop. For the above reasons, and because greater than 90% of the beef cows in the United States are bred by natural service, it is important that bulls be managed to optimize breeding performance. There are several factors that influence bull fertil¬ity. First, the bull must have developed properly and have reached puberty to be fertile. Second, the bull’s physical characteristics, such as scrotal circumference, mating abil¬ity, and semen quality, play a role in his fertility. Third, the bull’s libido and social dominance influence his fertility.


June 2008.